A 32-bit internet address
IPv4 identifies network interfaces with a 32-bit address commonly written as four decimal numbers separated by dots. An address such as 198.51.100.24 is easier for people to read than the underlying binary value.
Routers use address prefixes to decide where packets should travel. The address identifies a network location for routing; it does not by itself identify a person or device owner.
Public and private ranges
Public IPv4 addresses can be routed across the internet. Private ranges such as 10.0.0.0/8 and 192.168.0.0/16 are reused inside homes, companies, and other local networks.
A router commonly translates traffic from several private devices to one public address. This process is called Network Address Translation, or NAT.
Why IPv4 addresses are scarce
A 32-bit space contains about 4.3 billion values before reserved ranges are removed. Global internet growth exhausted the freely available supply, encouraging address transfers, sharing, and carrier-grade NAT.
IPv6 was created with a much larger address space, but IPv4 remains important because networks and services cannot all migrate at once.
IPv4 today
Many devices use dual stack and can reach destinations over IPv4 or IPv6. The protocol selected for a request depends on DNS records, local support, provider routing, and destination availability.